Recording apparatus

ABSTRACT

A recording apparatus, carrying out an image forming by ejecting ink from a recording head onto a recording paper transported by a recording paper transport unit, is characterized by transporting the recording paper while biasing the recording paper toward the recording paper transport by way of a recording paper bias unit equipped in the upstream direction of the recording paper transport, or equipping a paper guide upstream of the recording paper bias unit in a manner not contacting the recording paper transport unit, thereby passing the recording paper directly under the recording head without the recording paper coming in contact with the recording head even if the recording paper is curled, et cetera.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of Japanese Application No.2004-326675, filed Nov. 10, 2004, the contents of which are incorporatedby this reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a recording apparatus comprising meansfor preventing a recording paper from coming in contact with a recordinghead even if the recording paper lifts up due to the ejection of inkthereon or a paper with a propensity to curl is used.

2. Description of the Related Art

Inkjet recording apparatuses for carrying out a recording operation byejecting ink onto the recording face of a recording paper are widelyused. Such a recording apparatus generally comprises a recording headwith an ink ejection aperture forming surface for ejecting ink onto therecording face of a recording paper.

For instance, a recording head ejects ink droplets controlled based on adrive control signal supplied according to image data and formed eitherby the pressure of an electro-mechanical conversion body or the thermalenergy of an electro-thermal conversion body toward the recordingsurface of a recording paper through the ink ejection aperture formingsurface.

And, in an attempt to speed up a recording speed, there are relativelyhigh density recording heads formed in a matrix between 300 dpi and 600dpi for example and so called multi-nozzle, wide recording heads onwhich ink ejection apertures are formed across the entire recordingwidth of a recording paper, for instance the entire width of therecording paper. Incidentally, in order to place a recording head overthe entire area of recording, a structure placing a plurality ofrecording heads with a recording range which is equivalent to “a fewtenths” of the entire recording width. In such a case, the adoptedsystem is for securing a recording range without a gap across the entirerecording range by placing a plurality of recording heads in a zigzagpattern, in order to make the recording range continuous.

Meanwhile, in order to make a recording apparatus full color, four colorrecording heads, i.e., CMYK (cyan, magenta, yellow, and blackrespectively), need to be arranged serially in the transport directionof a recording paper. This results in the recording head area becomingwide in the direction of the recording paper transport. In such arecording apparatus, the distance between the recording face of arecording paper and the ink ejection forming face must be continuouslymaintained at a predetermined value in order to maintain a stablerecording.

The recording surface of a recording paper, however, sometimes lifts-updue to a wrinkle, curl or waviness caused by an absorption andsubsequent evaporation of moisture, and further to a wrinkle orwaviness, the so called cockling phenomenon, caused by the absorption ofink. Due to this, the recording paper comes into contact with therecording head, bringing about problems such as contamination of therecording head, recording head nozzle clogging, degradation of printquality, et cetera.

As countermeasures to such issues, methods have been proposed foravoiding a lift-up of recording paper, such as the one for holding downa recording paper by a hold-down member in an upstream part of therecording paper transport path, the one for maintaining flatness bysucking air through small holes in a platen member having a plurality ofsmall holes to keep the recording surface of a recording paper close tothe platen, and the one for transporting a recording paperelectro-statically attached to the transport belt.

And, a laid-open Japanese patent application publication No. 2001-293919has disclosed a method for preventing a sheet from coming in contactwith a recording head by the equipping of a hold-down roller on an edgepart of a carriage to which is mounted a recording head in order toconstrain a sheet from lifting-up.

In the meantime, a laid-open Japanese patent application publication No.2001-26154 has disclosed a paper hold-down mechanisms corresponding toeach of recording heads placed in a plurality of columns in thedirection of the recording paper transport.

SUMMARY OF THE INVENTION

The present invention is to provide a recording apparatus capable ofcarrying out a recording operation on a recording paper transportedrelatively to a recording part, with a capability of holding-down arecording sheet securely preventing it from lifting-up immediatelybefore the recording operation.

A recording apparatus according to one aspect of the present invention,having a recording head for forming an image by ejecting ink onto arecording sheet and a recording paper transport unit, being equippedopposite the recording head, for transporting a recording paper in aflat state, comprises: a recording paper bias unit equipped upstreamand/or downstream vis-à-vis the recording head for biasing the recordingpaper toward a recording paper transport unit; and a paper guideequipped upstream of the recording paper bias unit in a manner notcontacting the recording paper transport unit.

A recording apparatus according to another aspect of the presentinvention, having a recording head for forming an image by ejecting inkonto a recording sheet and a recording paper transport unit, beingequipped opposite the recording head, for transporting a recording paperin a flat state, comprises: a recording paper bias unit equipped in anupstream and/or downstream vis-à-vis each of a plurality of recordingheads placed in the direction of the width of the recording paper forbiasing the recording paper toward a recording paper transport unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a paper guide unit;

FIG. 2 is an illustrative side view of a recording apparatus accordingto an embodiment of the present invention;

FIG. 3 is an illustration showing the placements of sensors for arecording apparatus;

FIG. 4 is an illustrative top view of a platen unit;

FIG. 5 is an illustrative top view of a carriage;

FIG. 6 is a cross-sectional view of an arrangement of recording heads;

FIG. 7 is an illustrative side view of a carriage and a platen unit;

FIG. 8 is an illustration showing recording heads;

FIG. 9 is a diagonal view of a maintenance unit;

FIG. 10 is an illustrative top view of a paper guide unit;

FIG. 11A is an illustrative top view of a paper guide unit and FIG. 11Ba cross-sectional view thereof;

FIG. 12A describes a configuration of a paper guide rib and FIG. 12Bdescribes a state of recording paper curling;

FIG. 13A is a top view describing a configuration of a paper guide riband FIG. 13B a cross-sectional view thereof;

FIG. 14A and FIG. 14B describes a configuration of a paper guide roller;

FIG. 15 is a circuit block diagram of a control unit;

FIG. 16A is an illustrative top view of a paper guide for describing asecond embodiment and FIG. 16B a cross-sectional view of the paperguide;

FIG. 17 is a diagonal view of a paper guide unit for describing thesecond embodiment; and

FIG. 18A is an illustrative top view of a paper guide unit fordescribing a third embodiment and FIG. 18B a cross-sectional view of thepaper guide.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following is a detailed description of the preferred embodiment ofthe present invention referring to the accompanying drawings.

First of all, let one embodiment according to the present invention bedescribed while referring to FIG. 2 which is an illustrative side viewof a recording apparatus according to the present embodiment.

The recording apparatus 1 according to the present embodiment comprisesan apparatus frame (not shown herein), a paper feed unit 10, an imagerecording mechanism 20, an exit unit 50, a maintenance unit 60, an inksupply unit 70, a recording paper inversion unit 80, a control unit 90,and a paper guide unit 100 (not shown in FIG. 2).

[Paper Feed Unit 10]

The first description is of the above noted paper feed unit 10.

The paper feed unit 10 includes a recording paper tray 11, a pickuproller 12 and a registration roller pair 13. The recording paper tray 11is a recording paper housing unit for housing at least one sheet ofrecording paper. The present embodiment is configured so that therecording paper housing unit houses a plurality of cut sheets of paper.Note that the recording paper housing unit can also be configured tohouse a roll of recording paper.

The pickup roller 12 is a recording paper pickup mechanism for takingrecording paper out of the recording paper tray 11 one sheet at a time.And the pickup roller 12 is rotationally supported by the apparatusframe.

The registration roller pair 13 is a transport direction adjustmentmeans for positioning a recording paper taken out of the recording papertray 11, by the pickup roller 12, vis-à-vis the transport direction atthe time of recording an image (i.e., a recording paper transportdirection). The registration roller pair 13 is rotationally supported bythe apparatus frame. Note that the axis along the recording sheettransport direction is defined as the Y-axis (i.e., the horizontaldirection from the view of FIG. 2) of the present specification. And theaxis perpendicular to the Y-axis on the plane (i.e., the image formingplane), where an image is formed at the time of image recording on arecording paper, is defined as the X-axis (i.e., the directionperpendicular to the surface of FIG. 2). Furthermore, the axisperpendicular to the X-axis and Y-axis is defined as the Z-axis (i.e.,the vertical direction of FIG. 2). Therefore, the registration rollerpair 13 makes the width direction of a recording paper practically linedup with the X-axis and at the same time makes the directionperpendicular to the width direction of a recording paper lined up withthe Y-direction in the present embodiment. The registration roller pair13 is also a recording paper transport unit for transporting therecording paper after positioning it with the image recording mechanism20.

One roller of the registration roller pair 13 is rotationally supportedby the later described image recording mechanism 20, while the otherroller is rotationally supported by a lever operable by a user.Incidentally, the roller shown towards the top of FIG. 2 is a drivenroller, while the other roller towards the bottom is a drive roller inthe registration roller pair 13.

The lower drive roller of the registration roller pair 13 has itssurface coated by glass beads of particle sizes between 15 and 120microns by using an epoxy resin. By this surface treatment, while thetotal contact area with the recording paper is made small by the pointcontact of the glass beads, the pressing force per unit contact area islarge because the total pressing force does not change. Because of this,the drive roller of the registration roller pair 13 secures a necessarytransport force by the beads biting into the recording paper, whilereducing the total contact area therewith adhered by ink, therebysuppressing a transfer of ink from the recording paper and preventing animage degradation such as contamination with ink on the printing face ofthe recording paper even in a duplex printing.

Meanwhile, such a coating process of glass beads of a transport rollergives not only benefits to the registration roller pair 13 but also thesame benefits to a transport roller in the inversion mechanism used fora duplex printing, and to a transport roller and exit roller in the exitunit, et cetera. Moreover, the configuration is not limited to the glassbeads but can be applied to alumina (aluminum oxide) powder or ceramicpowder of similar particle sizes with the same expected benefits.

The registration roller pair 13 is placed within the size of a recordingpaper vis-à-vis the pickup roller 12 in the recording paper transportdirection so as to transport the recording paper from the pickup roller12 securely. This configuration makes a recording paper intransportation be in a state of the leading edge reaching theregistration roller pair 13 with the trailing edge being in the nip ofthe pickup roller 12. Therefore, the registration roller pair 13 isassisted by the pickup roller 12 in transporting the recording paper atleast until taking the leading edge thereof into the nip.

Incidentally, the path for a recording paper taken out by the pickuproller 12 being transported to the image recording mechanism 20 isdefined as the paper feed transport path in the present specification.By this configuration, the paper feed transport path extends from thepickup roller 12 to the border between the paper feed unit 10 and imagerecording mechanism 20.

Note that the above described pickup roller 12 is connected with theregistration roller pair 13 by a common drive power transmission system(not shown herein) which provides the drive power. The drive powertransmission system is connected to a motor (not shown herein) whosepower drives the aforementioned system. The motor is connected by anencoder for detecting the number of revolutions thereof. The motor andencoder are connected to the control unit 90 by which the drive thereofis controlled.

And the pickup roller 12 and registration roller pair 13 are configuredto connect or disconnect with the drive power transmission system by wayof clutches, respectively. Each of the clutches is further connected tothe control unit 90 which controls the switching on or off. Theserollers are configured as rotational around the X-axis according to thepresent embodiment.

Moreover, the paper feed unit 10 has a pickup sensor 14 a andregistration sensor 14 b between the pickup roller 12 and registrationroller pair 13 on the paper feed transport path as shown by FIG. 3. Thepickup sensor 14 a and registration sensor 14 b are detection means fordetecting a presence of absence of a recording paper at a predeterminedposition on the paper feed transport path.

The registration sensor 14 b is placed downstream of the pickup sensor14 a in the recording paper transport direction. The pickup sensor 14 aand registration sensor 14 b are connected to the control unit 90 so asto transmit the respective detection results thereto. Incidentally, alarge number of sensors are placed in the transport path of a recordingpaper as indicated by triangles (Δ) shown by FIG. 3, thereby detectingpositions of transported paper.

[Image Recording Mechanism 20]

The next description is of the image recording mechanism 20.

The image recording mechanism 20 comprises a platen unit 30 and an imagerecording unit 40. First, let the platen unit 30 be described byreferring to FIGS. 2 and 4. FIG. 4 is an illustrative top view of theplaten unit 30.

The platen unit 30 is a transport apparatus for transporting a recordingpaper fed out from the paper feed unit 10 at the time of recording animage. The platen unit 30 comprises a platen belt 31, a plurality ofplaten belt rollers 32, a platen frame 33, a platen suction unit 34 anda platen drive unit 36.

The platen belt 31 and a plurality of platen belt rollers 32 worktogether to constitute a belt conveyer for carrying a recording paperalong the Y-axis. In the present embodiment, the platen belt 31 is anendless belt. Note that the platen belt 31 and platen belt rollers 32set the transport direction of a paper at the time of recording. Thatis, the platen belt 31 and platen belt rollers 32 are assembled so as tobe able to transport a recording paper along the Y-axis across theirlength. Incidentally, FIG. 4 shows only the approximate half of theplaten belt 31 in the direction of the Y-axis for a better description.

The plurality of platen belt rollers 32 support the platen belt 31 so asto keep it in parallel with the X- and Y-axes within the area of theplaten belt 31 which faces the image recording unit 40. Meanwhile, arecording paper is transported by the platen belt 31 in theaforementioned area. Because of this, the area is called a platenrecording paper transport area which is indicated by a reference sign 31c as shown by FIG. 2. And at least one of the platen belt rollers 32 isconnected to a belt roller drive motor 32 a for rotating the platen beltrollers 32.

And, in order to prevent a recording paper from lifting-up, drivenrollers are placed in the positions facing, in terms of Z-axis, theplaten belt rollers 32 which are placed on both sides in terms ofY-axis. And an encoder for generating a head control pulse is installedon the platen belt roller 32 (i.e., the platen belt roller 32 indicatedon the left side of FIG. 2) on the opposite side of the platen beltroller 32 which is driven by a motor. And the belt roller drive motor 32a is equipped by a motor control encoder for controlling the motordrive.

The belt roller drive motor 32 a is also connected by a roller-useencoder 32 b for measuring the number of revolutions thereof. And thebelt roller drive motor 32 a and roller-use encoder 32 b are connectedto the control unit 90.

The width of the platen belt 31 (i.e., the size along the X-axis) is setat no less than the maximum width of a recording paper for use in animage recording. That is, if the recording apparatus according to thepresent embodiment accommodates a recording paper of A3 size, the widthof the platen belt 31 is set at no less than the width of A3 sizerecording paper. And the platen belt 31 is featured by a plurality ofsuction holes 31 a which are distributed evenly over the entiretythereof. Meanwhile, underneath the platen belt 31 is equipped by theplaten frame 33 for supporting the aforementioned platen belt 31 in aflat state.

The platen frame 33 supports the platen belt rollers 32 rotationally andat the same time retains the platen suction unit 34. The platen frame 33has a platen frame head facing surface 33 a which face the imagerecording unit 40. The platen frame head facing surface 33 a is parallelwith the XY plane, and is formed by a plurality of grooves 33 delongated along the Y-axis across the entire are a facing the platenbelt 31. At approximately the center of each of the grooves 33 d isfeatured a surface-facing hole 33 e which runs through to a laterdescribed platen chamber.

The platen frame head facing surface 33 a is also featured with platenguide holes 33 b in the area (i.e., non-platen areas) not facing theplaten belt 31 for positioning with the image recording unit 40. Thepresent embodiment is configured to comprise two of the platen guideholes 33 b, one each upstream and downstream of the direction of arecording paper transportation. FIG. 4 shows the platen guide hole 33 bupstream as the one indicated by the reference sign 33 b_1, while theone downstream is indicated by the reference sign 33 b_2.

The cross-sectional shape of the upstream platen guide hole 33 b_1 alongthe X- and Y-axes is approximately a circular. The downstream platenguide hole 33 b_2 is placed in the non-platen area on the opposite sideof the platen guide hole 33 b_1 in the direction of the X-axis. Theplaten guide hole 33 b_2 is an elongate hole with the same width as thediameter of the platen guide hole 33 b_1, and with the length beinglarger than the width. The longitudinal direction of the platen guidehole 33 b_2 makes an angle of approximately 45 degrees with the X-axis.

The platen frame 33 has two of a pair of platen drive unit guides 33 cfor guiding a platen drive unit 36. These platen drive unit guides 33 care equipped on the opposite sides of the platen frame head facingsurface 33 a the Z-axis. And a pair of the platen drive unit guides 33 cis equipped on both edges of the platen frame 33, respectively, in thedirection of the Y-axis as shown by FIG. 2. And a pair of the platendrive unit guides 33 c is equipped on both edges of the platen frame 33,respectively, in the direction of the X-axis. Each platen drive unitguide 33 c has a guide surface along the X- and Y-axes, and extends fromboth edges of the platen frame 33 by a predetermined distance.

The platen suction unit 34 is a negative pressure generation apparatusfor providing the platen frame head facing surface 33 a with a negativepressure. The platen suction unit 34 is fixed onto the platen frame 33on the opposite side vis-à-vis the platen frame head facing surface 33a. The platen suction unit 34 has a plurality of platen chambers.

These platen chambers have a platen chamber negative pressure generationsource for making the pressure of each chamber itself a negativepressure. The platen chamber negative pressure generation source is aknown negative pressure generation means such as a fan, and theconfiguration is such as to suck in air from the surface-facing holes 33e by the negative pressure of the platen chamber negative pressuregeneration source and thus suck a transported paper by way of the platenbelt 31. Therefore, the surface-facing holes 33 e are suction holes forsucking a recording paper. And each platen chamber negative pressuregeneration source is connected to the control unit 90 which controls thedrive.

The platen drive unit 36 is a drive apparatus for driving the platenframe 33 along the Z-axis (i.e., the vertical direction of FIG. 2). Theplaten drive unit 36 is positioned underneath the platen frame 33 andsupports it from below. The platen drive unit 36 has a pair of platendrive rotating shafts 36 a and four of a platen support unit 36 b.

The pair of platen drive rotating shafts 36 a is placed on either end ofthe platen unit 30 in the direction of the Y-axis so as to face eachother thereon as shown by FIG. 2. More specifically, one platen driverotating shaft 36 a (on the left side of FIG. 2) faces the other platendrive rotating shaft 36 a (on the right side of FIG. 2) in the directionof the Y-axis, and these two are positioned below either end of theplaten unit 30 in the direction of the Y-axis.

Each platen drive rotating shaft 36 a extends along the X-axis androtates around it. More specifically, each platen drive rotating shaft36 a is of a size along the X-axis such as to face the platen drive unitguides 33 c placed on both sides of the platen frame 33 in the X-axisdirection. The pair of platen drive rotating shafts 36 a is connected soas to transmit the mutual rotating force by way of a platen drive unitbelt 36 c. And one of the pair of platen drive rotating shafts 36 a isconnected by a platen drive unit motor 36 d whose rotation rotates theplaten drive unit belt 36 c so that the pair of platen drive rotatingshafts 36 a rotate synchronously. The platen drive unit motor 36 d isconnected to the control unit 90 by which the drive is controlled.

Meanwhile, each platen drive rotating shaft 36 a is fixed by a platensupport unit 36 b at the position corresponding to the platen drive unitguides 33 c, respectively, of the above described both ends in thedirection of the X-axis. Therefore, two of the platen support units 36 bare equipped for each platen drive rotating shaft 36 a. Each platensupport unit 36 b extends itself in the radial direction of the platensupport unit 36 b. One end of each platen support unit 36 b is fixed bythe platen drive rotating shaft 36 a as described above while the otherend is contacted with the platen drive unit guide 33 c. Therefore, thefour platen support units 36 b slide along the platen drive unit guides33 c according to the rotation of the platen drive rotating shafts 36 a.

By the above described configuration, the platen frame 33 changes itsposition in the direction of the Z-axis by the respective contactingpositions of the platen support units 36 b on the platen drive unitguides 33 c. Therefore, the platen frame 33 moves up or down along theZ-axis according to the drives of the platen drive rotating shafts 36 a.Incidentally, the platen frame 33 is placed in the highest position inthe direction of the Z-axis when the platen support units 36 b arepositioned in parallel with the Z-axis.

And the length of the platen support unit 36 b along the Z-axis isestablished so as to set the platen recording paper transport area 31 cof the platen belt 31 as the transport position of a recording paperfrom the paper feed unit 10 at the highest position. Furthermore, thelength that the platen drive unit guides 33 c along the Y-axis is set soas to lower the platen frame 33 to a predetermined position along theZ-axis.

The next description is of the image recording unit 40.

The image recording unit 40 is an ink ejection apparatus for ejectingink onto a recording paper. The image recording unit 40 comprises aplurality of recording head rows 41, a carriage 42 and a head coolingunit 49 as shown by a later described FIG. 5.

First, let the recording head rows 41 be described.

The recording head rows 41 are an aggregation of image recording unitsfor recording an image. The recording head rows 41 are equipped for eachcolor, extending to the same width, or more, as the maximum width of aused recording paper. Incidentally, the image recording unit 40according to the present embodiment has a total of four recording headrows, i.e., cyan (C), magenta (M), yellow (Y) and black (K) as shown byFIG. 2. And in the image recording unit 40, shown by FIG. 2, a suffixfor indicating a corresponding color (i.e., above described C, M, Y orK) is added to a reference sign for indicating each recording head row41 for description.

These recording head rows 41 are supported by a carriage 42 as shown byFIG. 5. FIG. 5 is an illustrative top view of the recording head rows 41mounted on the carriage 42. Note that in FIG. 5 one recording head row41 out of the four recording head rows 41 is omitted for the sake of thedescription. Each recording head row 41 is constituted by placing aplurality of later described recording head units 43 with theirlongitudinally aligned with one another.

The recording head rows 41 have a size, in the longitudinal direction,of no less than the width of a recording paper, so as to be able torecord an image across the entire width of the recording paper whenrecording an image. That is, if the image recording apparatus 1accommodates a recording of A3 size recording paper, the width of therecording head rows 41 is set at no less than the width of A3 sizerecording paper. The recording head row 41 according to the presentembodiment comprises six recording head units 43 as shown by FIG. 5.

The next description is of the carriage 42.

The carriage 42 comprises a head mount part 42 a for mounting therecording head row 41, a carriage holes 42B for exposing a recordinghead row 41 to a recording paper, a carriage positioning pin 42 c forpositioning the platen unit 30, a pair of paper feed roller linkageunits 42 d and frame contact flanges 42 h.

Let the head mount part 42 a be described first.

The head mount unit 42 a has a head mount surface 42 f for mounting therecording head row 41, and a recording paper facing surface 42 g (referto FIG. 6) which is the opposite surface to the head mount surface 42 f.The recording paper facing surface 42 g is the surface facing towards arecording paper at the time of recording an image. The head mount part42 a has a longitudinal direction and a width direction. Each recordinghead row 41 is placed on the head mount part 42 a so that thelongitudinal direction of the recording head row 41 and the widthdirection of the head mount part 42 a are practically in line with eachother as shown by FIG. 5. Note that these recording head rows 41 areplaced so as to maintain a distance D2 (refer to FIG. 5) between aneighboring recording head row 41 along the longitudinal direction ofthe head mount part 42 a. Incidentally the present specification refersto the longitudinal and width directions of the head mount part 42 a asthe longitudinal and width directions of the carriage 42. Also, in thedescription of the present specification, the longitudinal direction isalong the Y-axis and the width direction along the X-axis.

Next the carriage holes 42B are described.

The carriage holes 42B are featured in the head mount part 42 a inaccordance with the number of recording head rows 41. The presentembodiment is configured to feature four carriage holes 42B. Eachcarriage hole 42B comprises a plurality of exposure—use holes 42Ba,linked together, of a size allowing each recording head unit 43 to beexposed.

Each exposure-use hole 42Ba is placed in a position corresponding toeach recording head unit 43 when the recording head row 41 is correctlypositioned. The present embodiment is configured to connect sixexposure-use holes 42Ba together to form the each carriage hole 42Bwhich accordingly extends along the X-axis. Therefore, the longitudinaldirection of each exposure-use hole 42Ba is also practically in linewith the X-axis.

And, these carriage holes 42B are arranged in a predetermined intervalalong the Y-axis so as to achieve the above described location of therecording head rows 41. And the recording head units 43 constitutingeach recording head row 41 are suspended from the head mount part 42 aso as to protrude by the distance of D1 along the Z-axis from thecarriage holes 42B as shown by FIG. 6. Note that the neighboringrecording head rows 41 are separated from each other by the distance ofD2. Because of this, a space S (refer to FIG. 2) corresponding to thedistance D2 along the Y-axis and distance D1 along the Z-axis andextending along the X-axis is formed between neighboring recording headrows 41. FIG. 2 only shows one space S for clarity. The space S is thearea surrounded by the double-dotted lines.

Next, let the carriage positioning pin 42 c be described.

The carriage positioning pins 42 c protrude from the recording paperfacing surface 42 g as shown by FIG. 7. The carriage positioning pin 42c is configured to be insertable into the platen guide hole 33 bcomprised by the platen unit 30 when the image recording mechanism 20and the platen unit 30 are positioned in the image recording position(i.e., an image recording position).

More specifically, the carriage positioning pins 42 c are equipped bythe same number of the platen guide holes 33 b and are placed in aposition facing the respective platen guide holes 33 b. The presentembodiment comprises the carriage positioning pins 42 c equipped in thepositions facing the upstream platen guide hole 33 b_1 and thedownstream platen guide hole 33 b_2, respectively. Specifically, thecarriage positioning pin 42 c facing the downstream platen guide hole 33b_2 is placed in a position at the center thereof in the direction of X-and Y-axes. And the each carriage positioning pin 42 c has a lengthinsertable to the platen guide hole 33 b. Furthermore, the each carriagepositioning pin 42 c has practically the same diameter as the platenguide hole 33 b. Incidentally, the end of the each carriage positioningpin 42 c is featured with a taper (i.e., tapers off).

The next description is of each of the recording head units 43constituting each of the recording head rows 41.

The recording head unit 43 comprises at least one inkjet head 44. Thepresent embodiment is configured for the recording head unit 43 tocomprise two inkjet heads 44 as shown by FIG. 6.

First, let the comprisal of each inkjet head 44 be described.

Each inkjet head 44 comprises apiezoelectric body 46, a head base plate44 b, a nozzle plate 47, and a head ink distribution part 48 as shown byFIG. 6.

The inkjet head 44 comprised as described above constitutes therecording head unit 43 by adhering to another inkjet head 44 as shown byFIG. 6. When adhering to each other, the two inkjet heads 44 are adheredby the head base plate 44 b of each other. In such an assembled inkjethead 44, nozzle forming faces 47 d of respective nozzle plates 47 areset so as to be positioned on practically the same plane as shown byFIG. 6. At the same time, nozzle-side base plate faces 44 d of the headbase plates 44 b are placed so as to be flush with each other as shownby FIG. 6.

By the above described configured head base plate 44 b, the nozzleforming faces 47 d and two piezoelectric bodies 46 a guide groove 44 eis formed as shown by FIG. 6. The guide groove 44 e extends acrosspractically the entire longitudinal direction of the inkjet head 44,thereby guiding a movement of a later described maintenance suction unitof the maintenance unit.

And, when the recording head units 43 are assembled, the nozzle row ofeach inkjet head 44 constituting them is established in parallel witheach other as shown by FIG. 8. And the nozzle row of one inkjet head 44is shifted by a half of the pitch P of the nozzles 47 a in the directionof the array thereof, vis-à-vis the nozzle row on the other inkjet head44. This configuration enables the recording head unit 43 to record animage at 360 dpi, twice as much as the inkjet head 44 if it isconfigured for 180 dpi.

As described above, each recording head unit 43 constitutes the abovedescribed recording head row 41, together with other recording headunits 43 for each carriage hole 42B when placing the recording headunits 43 in the respective exposure-use holes 42Ba. At this point, letthe description of the recording head rows 41 be returned to.

Each recording head row 41 comprises a plurality of recording head units43 arranged in rows as described above. In such recording head rows 41,each recording head unit 43 is placed so as to partially overlap withthe adjacent recording head unit 43 in the direction of arranging therecording head units 43 (i.e., the longitudinal direction) as shown byFIG. 8. This configuration makes the nozzles of mutually adjacentrecording head units 43 in the arranging direction of the recording headunits 43 overlap with each other in the longitudinal direction of thenozzle row.

The overlapping area of adjacent nozzle rows is secured as indicated bythe reference sign A1 in FIG. 8, therefore the nozzle row of eachrecording head row 41 is configured without a gap along the entirelongitudinal direction of the recording head row 41. As such therecording head row 41 comprises the nozzles 47 a of a practicallyuniform pitch.

[Exit Unit 50]

The next description is of the exit unit 50.

The exit unit 50 is a mechanism for recording paper to exit afterrecording an image by the image recording mechanism 20. The exit unit 50comprises an exit unit transport roller pair 51, an exit unit exitroller pair 52, a path changeover unit 53, an exit auxiliary unit 54 andan exit tray 55 as shown by FIG. 2.

[Maintenance Unit 60]

The maintenance unit 60 comprises a plurality of maintenance units 61, aplurality of maintenance ink pans 62, a maintenance unit drive unit 63,a transport direction guide frame 64, four elevator guide frames 65, apositional detection units 68 a and 68 b as shown by FIG. 9.

First, let the maintenance units 61 be described.

The maintenance units 61 are equipped so as to correspond to thepositions of the four recording head rows 41. Specifically, themaintenance units 61 are arranged by being separated from one another bya predetermined distance in the direction of the Y-axis as with thearrangement of the recording head rows 41. Each maintenance unit 61 hasa plurality of maintenance suction units 61A and cap units 61C.Specifically, each maintenance unit 61 has a plurality of maintenancesuction units 61A and cap units 61C, both of which are arranged alongthe X-axis. The present embodiment is configured so that eachmaintenance unit 61 has the same number of maintenance suction units 61Aand cap units 61C as the number of the recording head units 43constituting each recording head row 41, i.e., six, respectively.

The each maintenance unit 61 has a base plate 61B for holding sixmaintenance suction units 61A. Each base plate 61B is fixed to themaintenance unit drive unit 63 and extends along the X-axis. On the baseplate 61B, each of six maintenance suction units 61A and six cap units61C are respectively arranged in the same way as the recording headunits 43 constituting the above described each recording head row 41.That is, when the maintenance units 61 are positioned vis-à-vis therecording head rows 41 at the time of a later described maintenance, theeach maintenance suction unit 61A is placed in the position facing thecorresponding recording head unit 43. Note that the six maintenancesuction units 61A are placed in the same position as the six cap units61C in the direction of the Y-axis, but displaced in the direction ofthe X-axis on the base plate 61B as shown by FIG. 9.

The each base plate 61B is also connected, by way of a suction tube61Ba, to a suction pump (not shown herein) for providing a suction forcefor the each maintenance suction unit 61A at the time of maintenance.And the base plate 61B has a flow path (not shown herein) for connectingthe suction tube 61Ba and each maintenance suction unit 61A. Therefore,the each maintenance suction unit 61A performs suction when the suctionpump is attains a negative pressure.

Next, let the maintenance ink pans 62 be described.

The maintenance ink pan 62 is an ink receiving pan for preventing inksplatter at the time of maintenance. The maintenance ink pans 62 arerespectively equipped for the same number of maintenance units 61 andplaced in positions corresponding to the respective maintenance units61.

Specifically, the each maintenance ink pan 62 is equipped on theopposite side of a recording head row 41 across the maintenance unit 61in the direction of Z-axis. The present embodiment is configured toequip the maintenance ink pan 62 below each maintenance unit 61. Thesize of the maintenance ink pan 62 along the X- and Y-axes is set to bethe same, or greater than, that of the maintenance unit 61. Eachmaintenance ink pan 62 is set for the position vis-à-vis the maintenanceunit 61 in the X- and Y-axes so as to be able to accommodate themaintenance unit 61. Also, the maintenance ink pan 62, while beingdescribed later, is set to a size in the direction of Y-axis so as to beable to take shelter in the above described space S between therecording head rows 41 at the time of recording an image. Specifically,the size of the maintenance ink pan 62 in the Y-axis is set to besmaller than the distance D2.

And the maintenance ink pan 62 is fixed to the maintenance unit driveunit 63. The maintenance ink pan 62 is set at the placement on theZ-axis at the time of the above described fixing so as to be able totake shelter in the above described space between the recording headrows 41. Specifically, the maintenance ink pan 62 is placed so that theposition of the lower end thereof (i.e., the end on the opposite sidevis-à-vis the recording head row 41) is a distance of greater than D2from the upper end of the transport direction guide frame 64 in theZ-axis direction. Therefore, when the upper edge of the transportdirection guide frame 64 comes into the proximity of the recording paperfacing surface 42 g, the maintenance ink pan 62 is never positionedbelow the edge of the recording head row 41 at the time of recording animage.

The next description is of the maintenance unit drive unit 63.

The maintenance unit drive unit 63 holds all the maintenance units 61 asdescribed above. Specifically, the maintenance unit drive unit 63 has apair of unit retention frames 63 b which extend along the Y-axis,thereby retaining each maintenance unit 61 from both ends along theX-axis. And the maintenance unit drive unit 63 has a pair of suctionunit drive mechanisms 63 a for making a unit retention frame 63 b drivenalong the X-axis. The pair of suction unit drive mechanisms 63 a fixedlysupports the unit retention frame 63 b at the front in terms of thedrive direction. And the unit retention frame 63 b on the rear side interms of the drive direction is supported by the suction unit drivemechanisms 63 a in a slidable manner. Therefore, the suction unit drivemechanisms 63 a press the unit retention frame 63 b on the front sidealong the X-axis at the time of driving, thus resulting in making allthe maintenance units 61 driven along the X-axis.

Note that the X-axis is the direction of a nozzle array on the each ofthe inkjet heads 44. Therefore, the pair of suction unit drivemechanisms 63 a is a maintenance suction unit drive mechanism for makingthe maintenance suction unit 61A move along the nozzle row of thecorresponding inkjet head 44. The pair of suction unit drive mechanisms63 a is configured to make at least the maintenance unit drive unit 63movable across the entirety of the inkjet head 44 in the direction ofthe nozzle row.

And when positioning the maintenance unit 61 at one end of the drivingrange along the X-axis, the suction unit drive mechanisms 63 a areplaced in the position facing the recording head unit 43 that each capunit 61 c corresponds to. The present specification defines theaforementioned position of the maintenance unit 61 as the home positionthereof.

The pair of suction unit drive mechanisms 63 a is connected to thecontrol unit 90 which controls the drive. Incidentally, the maintenanceunit drive unit 63 per se is supported in a movable manner vis-à-vis thetransport direction guide frame 64 in the Y-axis direction, hence makingit possible to make all the maintenance units 61 move in the Y-axisdirection as a result of the maintenance unit drive unit 63 moving inthe Y-axis direction.

The following descriptions are of the transport direction guide frame 64and the elevator guide frames 65.

The transport direction guide frame 64 has a pair of side walls 64Aalong the Y-axis. Both ends of each side wall 64A are featured with atransport direction guide groove 64Aa along the Y-axis. And thetransport direction guide frame 64 has a slide mechanism 64B forproviding driving power along the Y-axis. The slide mechanism 64B isconnected to the control unit 90 which controls the drive.

The four elevator guide frames 65 are support members for supporting thetransport direction guide frame 64 movably. These elevator guide frames65 are fixed to a frame (not shown herein) of the recording apparatus 1.Each of the elevator guide frames 65 is placed in a positioncorresponding to the transport direction guide groove 64Aa.

And each elevator guide frame 65 has an elevator guide groove 65 a alongthe Z-axis. And the each elevator guide groove 65 a is positioned withthe corresponding transport direction guide groove 64Aa, and is linkedwith the transport direction guide groove 64Aa by a link member such asa pin 65 b which is inserted so as to pass through these grooves. Bythis configuration, the elevator guide frame 65 supports the transportdirection guide frame 64 movably along the Y- and Z-axes as shown byFIG. 9. Incidentally, drive power is provided to the transport directionguide frame 64 by a slide mechanism 64B, thus allowing it to move alongthe Y-axis.

And the transport direction guide frame 64 is pressed by the platenframe head facing surface 33 a when the platen frame 33 moves upward asnoted in the above description of the platen unit 30. By thisconfiguration, the transport direction guide frame 64 moves in theZ-axis direction in accordance with a vertical movement of the platenframe 33. As such, since the transport direction guide frame 64 moveswith the platen frame 33, the size of the transport direction guideframe 64 in the Z-axis is set up so as not to obstruct the movement ofthe platen frame 33. In other words, the size of the transport directionguide frame 64 along the Z-axis is set so as not to contact the carriage42 when the platen frame 33 moves to a desired position on the Z-axis.

And the size of the transport direction guide frame 64 in the Z-axis isset so that the platen unit 30 is placed in the transporting position(i.e., an image recording position) of a recording paper at the time ofrecording an image when the upper end of the transport direction guideframe 64 is in contact with, or in proximity to, the recording paperfacing surface 42 g.

By this configuration, when being guided to one end of the transportdirection guide groove 64Aa along the Y-axis, the transport directionguide frame 64 is placed in a Y-axis suction setup position, while whenbeing guided to the other end, the transport direction guide frame 64 isplaced in a Y-axis retracted position. The Y-axis suction setup positionis the position where the maintenance unit 61 comes to the same positionas the recording head unit 43. In the Y-axis suction setup position,each maintenance unit 61 faces each inkjet head 44. Incidentally, thetransport direction guide frame 64 shown by FIG. 9 is positioned at theY-axis suction setup position along the Y-axis.

The above described Y-axis retracted position is the position where themaintenance unit 61 comes to the same position as the space S along theY-axis. That is, the Y-axis retracted position is the position along theY-axis where the maintenance unit 61 does not interfere with therecording head unit 43 even when the maintenance unit 61 moves along theZ-axis.

And when being guided to one end (i.e., the lower end as shown by FIG.9) of the elevator guide groove 65 a along the Z-axis, the transportdirection guide frame 64 is positioned at a Z-axis movable position,while when being moved to the other end (i.e., the upper end as shown byFIG. 9), the transport direction guide frame 64 is placed at a Z-axisretracted position. The Z-axis movable position is the position wherethe transport direction guide frame 64 does not interfere with therecording head unit 43 in the Z-axis direction. Therefore, the transportdirection guide frame 64 is movable along the transport direction guidegroove 64Aa in the Z-axis movable position.

The aforementioned Z-axis retracted position is the position where thetransport direction guide frame 64 is in the same position as the spaceS in the Z-axis. When the transport direction guide frame 64 is placedin the Y-axis retracted position on the Y-axis and in the Z-axisretracted position on the Z-axis, each of the maintenance units 61 isplaced within the applicable space S as shown by FIG. 7.

Note that the present embodiment is configured to provide the drivepower to the transport direction guide frame 64 from the platen frame33, but it is possible to provide the drive power by other independentdrive means.

The next description is of the positional detection units 68 (i.e., 68 aand 68 b).

The positional detection units 68 are means for detecting the positionof the maintenance unit 60. The positional detection units 68 comprisesa Y-axis suction position sensor 68 a (refer to FIG. 9), a Y-axisretracted position sensor 68 b (refer to FIG. 9), a Z-axis suctionposition sensor 68 c (refer to FIG. 7), a Z-axis retracted positionsensor 68 d (refer to FIG. 7) and an X-axis home position sensor 68 f(refer to FIG. 9). These sensors are connected to the control unit 90and transmit the respective detection result thereto.

[Paper Guide Unit 100]

The next description is of the paper guide unit 100.

The paper guide unit 100 comprises guide rollers 101 and 102, a paperguide frame 103, a paper guide rib 104 as shown by FIGS. 1, 10 and 11.Incidentally, FIG. 11A is an illustrative top view of a paper guide unitand FIG. 11B a cross-sectional view thereof.

The paper guide frame 103 is set up for the distance between the platenbelt 31 accurately as a result of a positioning unit (not shown herein)coming into contact with the platen frame 33 of the platen unit 30underneath the above described maintenance ink pan 62 of the maintenanceunit 60.

The guide roller 101 is equipped upstream of the recording papertransport direction of the recording head unit 43 and is rotationallysupported by the paper guide frame 103 either in contact with the platenbelt 31 or at a predetermined distance therefrom.

A guide roller 101 a is equipped for the recording head unit 43 (NB:shown by a recording head 43) positioned downstream of the recordingpaper transport direction among the head rows arrayed in a plurality ofcheckered patterns in the width direction of a recording paper, while aguide roller 101 b is equipped for the recording head unit 43positioning itself in the upstream of the recording paper transportdirection.

The guide roller 101 b is a roller of a split type having the same widthas the recording head 43 positioned upstream with respect to therecording paper transport direction. Note that the guide roller 101 bmay be configured by a single roller placed across the entire width of arecording paper.

The guide roller 102 is equipped downstream with respect to a recordingpaper transport direction of the recording head 43 and is rotationallysupported by the paper guide frame 103 so as to contact the platen belt31. The guide rollers 101 a and 101 b are respectively supported by thepaper guide frames 103 in a slidable manner in the Z direction, therebysecuring firmly the contact between the guide roller 101 and the platenbelt 31 even if flatness is not adequately secured by the platen frame33 of the platen unit 30 such as in the case of the platen frame 33being convex or concave, because each roller slides in the Z directionfollowing the form of the platen frame 33.

The surfaces of the guide rollers 101 and 102 are treated by an inkrepellent process such as fluoroplastic coating or silicone coating toprevent the ink from being transferred to the roller circumference as aresult of contacting the printing face of a recording paper or theplaten belt 31. That is, once a contaminant such as ink is transferredonto the roller circumference, the contact of the guide rollers 101 or102 with the recording paper surface which is transported subsequentlytransfers the ink onto the recording paper surface, thereby causing acontamination of the recording paper or a degradation of image quality.The above described processing prevents such problems.

The surface of the paper guide frame 103 facing the platen belt 31 isequipped by a paper guide rib 104. The configuration is such that thepaper guide rib 104 is equipped upstream with respect to the recordingpaper transport direction of the guide roller 101 as shown by FIG. 12A,and the distance to the platen belt 31 is large in the upstream of therecording paper transport direction, with the aforementioned distancegradually becoming smaller towards the downstream of the recording papertransport direction and that the distance to the platen belt 31 becomessmaller than the radius of the guide roller 101 at the point that theaforementioned distance becomes the smallest.

Incidentally, the paper guide rib 104 is configured to position itselfon the outside of a recording paper width direction for the downstreamas compared to the upstream of the recording paper transport directionas shown by FIG. 13. Such a configuration of the paper guide rib 104reverses along the width direction from one side to the other side ofthe center position of the recording paper width direction PWC.

And the guide rollers 101 and 102 are equipped with guide roller springs105 (refer to FIG. 11), thereby forcing them against the platen belt 31with a predetermined force in addition to the respective inherent weightof the guide rollers 101 and 102.

If a recording paper with a curl or wrinkle is transported to the imagerecording mechanism 20, the recording paper in many cases is sucked ontothe platen belt 31 by the suction force of the platen unit 30, therebysuppressing an uplift amount PH of the recording paper from the platenbelt 31 no more than the distance HG (i.e., a head gap) between thelowest surface of the recording head 43 and the upper surface of theplaten belt 31. However, some recording papers with a large curl orwrinkle uplift by an amount PH no less than the head gap HG even withthe suction of the platen unit 30 as shown by FIG. 12B.

Such a recording paper is pressed down at its leading edge by the paperguide rib 104 of the paper guide unit 100 and therefore the upliftamount PH of the leading edge of the recording paper becomes no morethan the radius of the guide roller 101 when the leading edge of therecording paper reaches the neighborhood of the guide roller 101,thereby being pressed down to the platen belt 31 smoothly by the guideroller 101.

The recording paper pressed against to the platen belt 31 by the guideroller 101 has an uplift amount PH becoming larger as the leading edgethereof leaves the nip point of the guide roller 101, but by the timethe uplift amount PH becomes larger than the head gap HG, the leadingedge of the recording paper has passed the bottom surface of therecording head 43, and therefore the recording paper never comes intocontact with the recording head, thus enabling a printing and feeding ofthe paper.

Meanwhile, when using a recording paper with a large curl or wrinklecausing an uplift amount PH to exceed the head gap HG, the trailing edgeof the recording paper can possibly come into contact with the recordinghead 43. The trailing edge of the recording paper, however, does notcome into contact with the recording head 43 because the trailing edgeof the recording paper is forced down onto the platen belt 31 by theguide roller 102, thus enabling a printing and feeding of the paper.

The paper guide unit 100 is placed so as to accommodate, by a pairthereof, each of the recording head rows 41 arranged in the sequence ofK, C, M, and Y in the recording paper transport direction. Such aplacement makes it possible to force down securely a recording paperwith a curl onto the platen belt 31 immediately in front of the eachrecording head.

Meanwhile, in the case of printing in a high temperature and highhumidity environment, a recording paper absorbs moisture from its edgesand swells. In such an event, the difference in moisture absorptionconditions (that is, nearby edges absorb a greater amount of moisture,thus causing more swelling, than the central parts) generates wrinklesmainly near the edges of a recording paper.

The mechanism of wrinkle generation due to such swelling is basicallythe same as the mechanism of wrinkle generation due to permeation of inkinto a recording paper.

This kind of wrinkle cannot be eliminated simply by pressing down with aroller, et cetera, because it is a wrinkle generated due to thedifference in the degree of swelling within a recording paper.

Accordingly, the guide rollers 101 and 102 are featured with one or aplurality of grooves on its circumference as shown by FIG. 14A and FIG.14B, thereby distributing wrinkles caused by moisture absorption or inkpermeation in order to reduce the height of wrinkles as a whole, orthereby gather wrinkles in a small part where wrinkle generation causesrelatively small adverse effect, and enabling the prevention of failureoccurrence such as a printing head coming into contact with a recordingpaper due to a wrinkle.

[Control Unit 90]

The control unit 90 is constituted by a computer including a CPU, timer,ROM, RAM, et cetera as shown by FIG. 15. The control unit 90 isconnected to the above described paper feed unit 10, image recordingmechanism 20, exit unit 50, maintenance unit 60, ink supply unit 70 andrecording paper inversion unit 80, respectively, controlling the drivingof the aforementioned components.

More specifically, the control unit 90 is connected to the pickup sensor14 a and registration sensor 14 b in the paper feed unit 10. The controlunit 90 controls the drives of the pickup roller 12 and the registrationroller pair 13 by way of the drive power transmission system.

The control unit 90 is also connected to the belt roller drive motor 32a, roller-use encoder 32 b, platen chamber negative pressure generationsource 34 a, platen drive unit motor 36 d and image width detectionunit, and controls the aforementioned components.

The control unit 90 is also connected to the recording head 43, coolingfan 49 a, path changeover unit 53, bend wing 54 b, suction unit drivemechanism 63 a, suction unit pump 66 and slide mechanism 65B, andcontrols the aforementioned components.

The control unit 90 is further connected to respective sensors 68 athough 68 e of the position detection unit, and respective pieces ofpositional information are sent over from these sensors. And the controlunit 90 is connected to various rollers such as the exit unit exitroller pair 52, various valves, pumps, et cetera, and carries out therespectively corresponding controls.

[Operation]

The next description is of an operation of the image recording apparatus1 configured as described above.

First, when recording an image by the image recording apparatus 1, thecontrol unit 90 receives an input of image data by way of an interface(not shown herein). Then the control unit 90 carries out an imagerecording process based on the input image data.

In this event, the control unit 90 outputs a drive instruction to theslide mechanism 65B and platen drive unit motor 36 d to let the imagerecording apparatus 1 retract the maintenance unit 60. And the controlunit 90 confirms the retraction of the maintenance unit 60 by way of theZ-axis retracted position sensor 68 d and Y-axis retracted positionsensor 68 b.

Following the maintenance unit 60 completing a retraction, recordingpaper pickup is initiated. The control unit 90 outputs a driveinstruction to the drive power transmission system so as to turn on aclutch and rotate the pickup roller 12.

The pickup roller 12 picks up a recording paper from the recording papertray 11 to transport it to the registration roller pair 13 along therecording paper transport direction.

Then, in a predefined time after receiving a detection signal from theregistration sensor 14 b, the control unit 90 starts driving theregistration roller pair 13. By so doing, the recording paper istransported to the area of the image recording mechanism 20.

Also in the image recording process, the control unit 90 outputs a driveinstruction to each platen chamber negative pressure generation source34 a of the platen unit 30 before a recording paper is transported fromthe paper feed unit 10. Also in this event, the control unit 90 outputsa drive instruction to the belt roller drive motor 32 a to drive theplaten belt 31.

When a recording paper is transported from the paper feed unit 10 to theimage recording mechanism 20 (i.e., at the beginning of atransportation), the leading edge of the recording paper is sucked andretained by the platen belt 31. This prevents the recording paper fromlifting up from the platen belt 31. The sucked and retained recordingpaper is moved along in the recording paper transport direction by theplaten belt 31 at a predetermined speed.

Then, when the leading edge of the recording paper is transported to theposition that faces the recording head row 41, the control unit 90outputs an image recording instruction to the image recording unit 40.By so doing, each inkjet head 44 starts ejecting ink onto the recordingpaper. The ink ejection is carried out by each recording head row 41which extends across the entire width of the recording paper, andtherefore a single ejection is capable of recording over the entirewidth. The platen unit 30 transports the recording paper along theY-axis in association with the image recording. By this processing theimage is recorded sequentially in the longitudinal direction of therecording paper.

In this event, the leading edge of the recording paper is pressed downby the paper guide rib 104 of the paper guide unit 100 so that that thelifting amount PH of the leading edge of the recording paper becomes nomore than the radius of the guide roller 101 when the leading edge ofthe recording paper reaches the neighborhood of the guide roller 101,thereby being pressed down onto the platen belt 31 smoothly by the guideroller 101 in the present embodiment.

The recording paper pressed down onto the platen belt 31 by the guideroller 101 has a lifting amount PH becoming larger as the leading edgeleaves the nip point of the guide roller 101, but the leading edge ofthe recording paper passes through the bottom surface of the recordinghead 43 before the lifting amount PH becomes larger than the head gapHG. Therefore, even in the case of a recording paper with a large curlor wrinkle, the lifting amount PH of the recording paper is no more thanthe head gap HG, hence feeding the recording paper without coming intocontact with the recording head.

Then, as the recording paper passes through all the recording head rows41, the image recording is completed. As described above, the imagerecording apparatus according to the present embodiment is configured toplace the guide rollers 101 and 102 in upstream and downstream of therecording head, respectively, for each recording head which is placed inthe entire recording area, thereby preventing a recording paper fromcoming in contact with the recording head even if the recording paperhas a curl, wrinkle or cockling. This makes it possible to record on,and transport, the recording paper without allowing an occurrence of apaper jam or an ink contamination on the recording paper.

It is also configured to place the paper guide rib 104 upstream of eachguide roller so that the distance to the platen belt 31 at the narrowestpoint is smaller than the radius of the paper guide roller 101, therebymaking it possible to press a large curl, larger than the radius of theguide roller 101, down onto the platen belt without riding up the guideroller 101.

Also in a configuration which places a plurality of recording heads in acheckered pattern in the width direction of the recording paper, guiderollers are divided correspondingly and they are placed immediatelybefore the recording head 43 corresponding thereto as guide rollers 101a and 101 b. Because of this, the distance between each of therespective separate recording heads 43 and the guide roller 101 a or 101b, hence a recording paper with a curl, et cetera, does not come intocontact with the recording head 43.

Furthermore, a plurality of rollers is movable up and down against thebelt platen independently. This makes the rollers move along theprotrusions and indentations of the belt platen surface and recordingpaper and therefore a curled leading edge of a recording paper ofvarious thickness or size can be pressed down onto the belt platen.

The next description is of a second embodiment while referring to FIGS.16 and 17. FIG. 16A is an illustrative top view of the paper guide unitand FIG. 16B a cross-sectional view of the paper guide unit.

FIGS. 16 and 17 show a configuration with the guide rollers 101 and 102being removed from the configuration of the first embodiment and arecording paper with a curl or wrinkle is guided and transported by apaper guide rib 104 only. Incidentally, the configuration is such thatthe paper guide rib 104 is positioned on the outside in terms of therecording paper width direction in the downstream as compared to theupstream of the recording paper transport direction as described above.The configuration of the paper guide rib 104 is mutually reversed at thecenter position PWC of the recording paper width direction.

The present embodiment does not comprise guide rollers 101 or 102, thusno function of pressing a recording paper down onto the platen belt 31,but the configuration is such that the distance between the edge of thepaper guide rib 104 (i.e., the utmost downstream in terms of therecording paper transport direction) and the platen belt 31 is set at nomore than the head gap HG, hence the paper guide rib 104 forces a curlor wrinkle of a recording paper, which is not adequately sucked by thesuction force of the platen unit 30, down onto the platen belt 31.

The recording paper forced down onto the platen belt 31 by the edge partof the paper guide rib 104 is printed on and fed through without comingin contact with the recording head 43.

Such a configuration which places the paper guide for forcing arecording paper in the platen direction for each of the recording headsplaced across the entire area of recording upstream of the recordinghead, thereby making it possible to feed paper without a recording paperwith a curl, wrinkle or cockling coming in contact with the recordinghead 43. This prevents an occurrence of paper jam or ink contaminationon a recording paper.

The next description is of a third embodiment while referring to FIG.18. Note that FIG. 18A is an illustrative top view of a paper guide unitand FIG. 18B a cross-sectional view of the paper guide.

As shown by FIG. 18, the present embodiment is configured to mount aguide plate 108 onto the maintenance unit 60 directly. The guide plate108 has openings for the respective parts of recording heads 43 and allthe other part facing the platen belt 31 by keeping the distance smallerthan the head gap HG.

The above described configuration also makes it possible to retain alifting amount PH of a recording paper with a curl or wrinkle at nolarger than the head gap HG.

Note that the above descriptions are specific to the preferredembodiments according to an example of the present invention which,however, includes all possible embodiments to be carried out within thescope of the present invention, in lieu of being limited by the abovedescribed embodiments.

As such, the present embodiment is configured to place paper suppressionrollers upstream and downstream of the recording heads, for each of therecording heads arranged across the entire recording area, therebymaking it possible to prevent a recording paper from an inkcontamination and improve a print quality without allowing a recordingpaper having a curl, wrinkle or cockling to come in contact with therecording head.

And a lifting amount of a recording paper having a curl, wrinkle orcockling is suppressed by the paper guide, even the lifting amount of arecording paper having a large curl is suppressed to the head gap orless, thus the transport of a recording paper is carried out stably, alifting of a recording paper is held down, a contamination of arecording paper or a nozzle clogging of a recording head is preventedand paper jams are reduced.

1. A recording apparatus, comprising: a recording head row including aplurality of recording heads arranged to form an image by ejecting inkonto a recording paper, the recording head row extending in alongitudinal direction across a width of the recording paper, and eachof the recording heads partly overlapping an adjacent recording head inthe recording head row in the longitudinal direction; a recording papertransport unit arranged opposite the recording heads for transportingthe recording paper in a flat state; a plurality of recording paper biasunits, each arranged upstream of and in alignment with at least one ofthe plurality of recording heads and proximate the at least onerecording head to bias the recording paper toward the recording papertransport unit and thereby prevent the recording paper from lifting offof the recording paper transport unit before the recording paper passesby the at least one of the recording heads.
 2. The recording apparatusaccording to claim 1, further comprising a paper guide arranged upstreamin a recording paper transport direction vis-à-vis said recording paperbias unit so as not to contact said recording paper transport unit forguiding a leading edge of the recording paper toward the recording paperbias unit.
 3. The recording apparatus according to claim 2, wherein:said recording paper bias unit comprises a roller which is drivenvis-à-vis recording paper transportation.
 4. The recording apparatusaccording to claim 1, wherein: said recording paper bias unit comprisesa paper guide which does not contact said recording paper transportunit.
 5. The recording apparatus according to claim 3, wherein each ofsaid rollers has a same width as an aligning one of the recording heads.6. The recording apparatus according to claim 2, wherein: said recordingpaper bias unit comprises a roller which is driven vis-a-vis recordingpaper transportation and wherein a distance between said paper guide andthe recording paper is smaller than a radius of said roller.
 7. Therecording apparatus according to claim 6, wherein each of said rollershas a same width as an aligning one of the recording heads.
 8. Therecording apparatus according to claim 1, wherein: said recording paperbias unit comprises a roller which is driven vis-à-vis recording papertransportation.
 9. The recording apparatus according to claim 1,wherein: said recording paper bias unit is treated by an ink-repellentprocessing at least for surfaces facing, or contacting with, therecording paper.
 10. The recording apparatus according to claim 8,wherein each of said rollers has a same width as an aligning one of therecording heads.
 11. The recording apparatus according to claim 1,wherein the recording heads are arranged to eject a same color ink ontothe recording paper.
 12. A recording apparatus comprising: a recordinghead row including a plurality of recording heads arranged to form animage by ejecting ink onto a recording paper, the recording head rowextending in a longitudinal direction across a width of the recordingpaper, and each of the recording heads partly overlapping an adjacentrecording head in the recording head row in the longitudinal direction;a recording paper transport unit arranged opposite the recording headsfor transporting the recording paper in a flat state; and a plurality ofbiasing means each arranged upstream of and in alignment with at leastone of the recording heads and proximate the at least one of therecording heads for biasing the recording paper toward the recordingpaper transport unit and thereby prevent the recording paper fromlifting off of the recording paper transport unit before the recordingpaper passes by the at least one of the recording heads.
 13. Therecording apparatus according to claim 12, wherein said biasing meanscomprise rollers.
 14. The recording apparatus according to claim 13,wherein each of said rollers has a same width as an aligning one of therecording heads.
 15. The recording apparatus according to claim 13,wherein said biasing means comprises paper guide ribs.
 16. The recordingapparatus according to claim 13, wherein the recording heads arearranged to eject a same color ink onto the recording paper.